The present invention relates to a flying head slider for stably flying a magnetic head off the surface of a magnetic disk.
In conventional magnetic disk apparatus, there has been widely used a flying head slider as disclosed in U.S. Pat. No. 3,823,416 in which at least two straight rail surfaces form air bearing surfaces. A flying head slider of the type having a pair of side rails spaced from a rear end of the slider and one center rail disposed between the side rails, with a magnetic head mounted at a rear end of the center rail, as disclosed in U.S. Pat. No. 4,894,740, has also been put into practice.
Meanwhile, a magnetic resistance effect type head and a recording method wherein recording density is almost the same from inner periphery to outer periphery of a magnetic disk (hereinafter referred to as a multi-zone recording method) are beginning to be used, aiming at higher recording density.
In a magnetic resistance effect type head, recording is made by using an induction type magnetic head device comprising a core and a coil as usual, but reproduction is made by utilizing the property of a magnetic resistance effect film that its electric resistance varies depending on the intensity of magnetic flux penetrating the film. Therefore, the magnetic resistance effect type head has not the property that reproduction output increases at higher relative speed between a magnetic head and a magnetic disk medium, as has been obtained in the conventional induction type magnetic head. It is thus not expected in the magnetic resistance effect type head to reproduce data more advantageously in outer periphery than inner periphery of the disk.
Also, because recording density is almost the same from inner periphery to outer periphery of a magnetic disk in the multi-zone recording method, the method is not compatible with such a conventional design concept that recording/reproducing can be made in the outer periphery even if the flying height is fairly larger in the inner periphery than in the outer periphery of the disk.
The foregoing situation in art has raised a necessity of keeping the flying height substantially constant from inner periphery to outer periphery of a magnetic disk, in order to maximally utilize capabilities of the magnetic resistance effect type head and the multi-zone recording method. The above-mentioned magnetic head sliders of prior art are disadvantageous in that, because positive pressure generating bearings are used, the flying height varies with changes in the circumferential speed of a disk, and that the flying height becomes largely different between the inner periphery and the outer periphery if those prior art sliders are used in magnetic disk apparatus of linear actuator type. Also, if those prior art sliders are used in magnetic disk apparatus of rotary actuator type, the flying height can be kept nearly constant from the inner periphery to the outer periphery by combining the property that the flying height decreases with a yaw angle produced and the property that the flying height increases at the higher circumferential speed. However, when an access operation is made at high speeds in magnetic disk apparatus, a slider is moved at high speeds in a transverse direction thereof and brought into the same condition as where a yaw angle is apparently produced. This raises another disadvantage in the above prior art sliders that the flying height is reduced during the access operation. Thus, rotary actuator type apparatus using the above prior art sliders can keep the flying height nearly constant from the inner periphery to the outer periphery, but a reduction in the flying height during the access operation cannot be overcome so long as the apparatus design employs the property that the flying height decreases with a yaw angle produced.
Sliders of the type that the flying height is kept constant from the inner periphery to the outer periphery by utilizing a negative pressure instead of utilizing the property that the flying height decreases with a yaw angle produced, are disclosed in U.S. Pat. No. 4,475,135 and U.S. Pat. No. 4,555,739. In these prior arts, the slider has a cross rail for generating a negative pressure which is balanced with a positive pressure generated by a positive pressure generating rail, enabling the flying height to be kept constant from the inner periphery to the outer periphery. However, this type slider has drawbacks that the flying height decreases largely with a yaw angle produced, and that dust and dirt are apt to gather and a high degree of reliability is hard to maintain, because the cross rail and tapered portions are provided all over the width of the slider at its front edge.
On the other hand, a reduction in the flying height with a yaw angle produced can be effectively suppressed by a method of arranging a rail obliquely with respect to the direction of air inflow, as embodied in a slider having a rail central portion narrower than rail front and rear portions as disclosed in Japanese Patent Unexamined Publication No. 60-101781, and a triangular slider as disclosed in Japanese Patent Unexamined Publication No. 61-230687 corresponding to U.S. Ser. No. 718,910, filed on Apr. 2, 1985. As a method of suppressing intrusion of dust and dirt by utilizing a negative pressure, it is effective to form a slider into a wedge-like shape as disclosed in U.S. Pat. No. 4,644,641. However, those prior art sliders have a limitation in improving flying stability in the rolling direction and hence accompany a problem in reducing not only the slider size but also the flying height. The flying stability in the rolling direction is improved by mounting a magnetic head at a rear end of a center rail and forming side rails to be spaced from a rear edge of the slider, as disclosed in Japanese Patent Unexamined Publication No. 1-298585 and U.S. Pat. No. 4,894,740. With the prior arts, as mentioned above, the techniques effective in overcoming the individual problems are disclosed, but any of the prior art sliders has difficulties in overcoming all the problems in a well balanced manner.
The present invention is to provide a magnetic head slider which can effectively overcome the above-mentioned problems in the prior art and to realize all the purposes of keeping the flying height almost constant from inner periphery to outer periphery of a magnetic disk, suppressing a reduction in the flying height with a yaw angle produced and hence a reduction in the flying height during access operation, suppressing intrusion and compression of dust, and reducing size of the entire slider while ensuring flying stability in up-and-down, pitching and rolling directions, and which can maximally utilize capabilities of the magnetic resistance effect type head and the multi-zone recording method.